The invention pertains to sensors for measuring voltages. Particularly, it pertains to fiber optic sensors, and more particularly to such sensors not having a ground reference for measurements, and more particularly to such sensors have a time delayed self-reference.
One of the main difficulties of optical methods of sensing high voltage is related to the fact that optical sensors are typically inherent electric field sensors. In order to measure a ground-to-line voltage, the typical optical sensor needs to integrate the electric field over the entire distance from the ground to the voltage line. This approach requires that the entire voltage be dropped across the optical sensor. This is difficult and dangerous for application areas such as high voltage transmission lines. One solution to this problem is to implement a form of field control (e.g., capacitive dividers) such that a local electric field spanning the optical sensor is a fixed or a well-known proportion of the entire field. However, the latter approach adds considerable complexity and uncertainty to voltage measurements.